IT WAS ORIGINALLY to have been a rather relaxed and limited affair. The men who lead the four major military powers of the Atlantic were to meet for a couple of days of strategic conversation on Guadeloupe. The plans called for a little SALT, and a lot of sociability and sunshine.

But when people at that rank meet, it's hard to keep the agenda simple. The White House says that the four will not discuss economic subjects. But that will be strictly accurate, we assume, only if you do not call Iran's vanishing oil an economic subject.

This sort of meeting always serves the valuable purpose of forcing busy men to give a few hours' concentrated attention to the anxieties of their allies, as expressed by the allies themselves rather than by several ranks of intermediaries and emissaries. That makes the Caribbean exercise worthwhile, regardless of declarations reached or commitments made. But that last phrase -- the bit about commitments made -- touches a sensitive point. The last time these four men met was in July in Bonn, along with the heads of the Japanese, Italian and Canadian governments. They all made a number of firm undertakings about economic growth, trade and oil. Unfortunately, the United States has not done very well in keeping the highly explicit promises that it made regarding oil. It said that it would keep oil imports, last year and this, below the 1977 level; by late last year, they were well above 1977 levels, and climbing rapidly.

With the drastic drop in Iranian production, U.S. performance on oil imports becomes a matter of particularly sharp concern to the Europeans. The uncontrollable American thirst for foreign oil is exerting a rising pressure on the supplies that all of the industrial world must share. Oil consumption in the major European countries is just about where it was five years ago. But in the United States it's up substantially. If Iran exports little or no oil over the coming months, the industrial countries have two choices. They can either begin bidding against each other, driving the price to new heights. Or they can agree to cut back on their demands, distributing the shortfall among themselves by common consent. If the four eminent men at Guadeloupe do not reach this issue, they will have evaded the most urgently dangerous question now confronting them.

But if there's to be discussion of oil, shouldn't the other three of the seven -- Japan, Italy, Canada -- be there to share in the sunshine? A meeting of the United States, Britain, France and Germany would make sense if the topic was to be strategic arms and NATO. It makes less sense if the talk is to get into oil-sharing agreements. Japan is, after all, second only to this country as an importer of oil. Perhaps the best that can be said is that things have gotten a bit unraveled, and governments are going to have to be tolerant of each others' failures of etiquette.

The recent record for joint action among the four nations represented at Guadeloupe is not very impressive. None of the four has been showing much inclination to inconvenience itself greatly for any common purpose. But alliances among democracies in general, and these four in particular, seem to work well only under strees. They are at their best in crises. The four men enjoying the Caribbean sun hardly need to be reminded that unexpected events in Iran may shortly impose on them an interesting test of that proposition.